Self-stick labels made from a film web or backing carrier coated with a pressure-sensitive adhesive are usually composed of laminates of
1. a film web which acts as the imprintable backing carrier or visible web and is coated with a pressure-sensitive adhesive, and PA0 2. a release web or protective layer for the adhesive, which is coated with a low-surface-tension substance such as a silicone, and allows the label to be detached smoothly when required for use.
Laminates of this type are prepared in the form of large rolls and are then cut into rolls of smaller width or into sheets of suitable size. The laminates are then imprinted, and the desired outline of the individual labels which are formed from the backing carrier is achieved by stamping, only the backing carrier and not the release web being cut. The surplus backing carrier material between the labels is then peeled away from the release web as a net and is discarded. The resulting roll comprising the release web and the individual labels attached thereto is fed into suitable machines, and the labels are applied at a high rate to the objects which are to be labeled.
Low-cost paper is suitable for use as the backing carrier only for low quality labels.
Metal foils or thermoplastic polymer films are therefore also used for the film web, but these materials also have certain deficiencies with respect to processing and/or stability. Films made of the frequently used plasticized polyvinyl chloride contain up to 20% by weight of a monomeric plasticizer and are difficult to imprint, shrink with aging and alter important properties due to the interaction of the pressure-sensitive adhesive with the plasticizer. Polyolefins, such as polyethylene or polypropylene, are likewise difficult to imprint. Cellulose acetate is not moisture-resistant and has poor dimensional stability. Polystyrene has inadequate processing properties and a low resistance to solvents. Polyethylene terephthalate has disadvantages with respect to imprintability and, because of its rigidity, is not sufficiently adaptable to other than flat or cylindrical surfaces.
It has therefore already been proposed to prepare backing carriers of, for example, self-stick labels from radiation-curable polymers (U.S. Pat. Nos. 4,008,115; 4,022,926; 4,219,596 and 4,253,899). However, radiation-curable polymers of this type yield highly crosslinked films which are therefore difficult to imprint, are too rigid and are often brittle. Zimmermann (U.S. Pat. No. 4,818,610 and published European Application 0,305,161) uses other acrylate polymers.